The proposed research describes an in vivo and in vitro study of positive and negative cell-mediated immune (CMI) regulation by biochemically purified soluble factors from normal and tumor-bearing host (TBH) macrophages (M phi). M phi cell lines (P388Dl, J774, and RAW 264) will be screened and used in conjunction with "normal" host M phi, should their activities be identical, since they afford increased amounts of M phi-derived material. The objectives are fourfold: a) To determine if normal and TBH M phi supernatants can be separated into individual enhancing and inhibitory moieties. Biochemical techniques previously employed in the characterization of suppressor T (Ts) cell inhibitor factor will be used (e.g., ion exchange and gel filtration chromatography, slab gel electrophoresis). b) To determine if factor(s) from normal and TBH M phi differ in their ability to enhance or inhibit T cell in vitro activity. In vitro activity will be measured by comparing T cell blastogenesis, induced by mitogen or allogenetic M phi-depleted lymphocytes, will be measured by 3H-thymidine uptake. Lymphocyte-mediated cytotoxicity will be measured by release of 51Cr from allogeneic targets. c) To compare in vivo immunoregulatory properties of purified normal and TBH M phi factor(s). To mimic the in vivo milieu, cell-impermeable chambers containing normal or TBH M phi will be implanted. Subsequent in vitro T cell blastogenesis assays will assess M phi factor influence. Using inoculation of M phi supernatant factors, in vivo CMI regulation will be measured by comparing the ability of treated and control populations to (1) reject an allogeneic skin graft; (2) reject a challenge tumor cell inoculation following removal of the primary syngeneic tumor; (3) respond to a challenge dose of DNFB after primary topical application; and (4) manifest concomitant immunity. d) To determine if the previously isolated Ts cell factor shows inhibitory activity following addition of M phi enhancing factor(s)-- regulatory hierarchy(?).